#define  _CRT_SECURE_NO_WARNINGS  1
#include <stdio.h>
int main()
{
	int i = 0, n = 0;
	int s = 0;

	for (i = 0; i < 5; i++)
	{
		scanf("%d", &n);
		s = s + n;
	}
	printf("%.1lf", s / 5.0);

	return 0;
}